To rig a weight-painted 3D model, bind the model to an armature (skeleton) first, then use weight painting tools to assign how much each bone influences vertices.
Weight painting controls deformation: White means full bone influence, black means none, and grays blend (ideal for natural bends like elbows). Software like Blender or Maya uses brush tools—start with auto-weights (a quick base) then refine to fix stretching or clipping.
For beginners, try a simple model (e.g., a character’s arm) and use the "smooth" tool to even weights—this eases refining and helps avoid unnatural movements.